It is known in the assembly of insulating glass panes whose glass panels are held apart and adhered to one another by a plastic spacer, first to apply the strand-like spacer onto a first of the two glass panels along its edge, such that a gap remains between the ends of the spacer in the vicinity of a corner of the glass panel, and is not closed until later, after assembly and pressing of the insulating glass pane. Closing must be performed very carefully so as not to leave open any gap through which moisture might penetrate into the interior of the insulating glass pane. It is known to close the gap by passing a heated shaped element around that end of the plastic spacer at which the gap is located, so that the thermoplastic material of which the spacer is made softens, and the two ends of the strand of which it is constituted join one another to form a continuous frame. This entails problems in practical implementation, however: the abutting surfaces between the two ends of the spacer cannot be reached with the heated shaped element, and it is also difficult to exert pressure thereon because it is possible to act on the spacer only from outside, i.e. parallel to the abutting surfaces. It becomes particularly difficult to close the gap when it is not already quite narrow, since then the action of a heated shaped element alone is not sufficient, and instead additional thermoplastic material must be introduced into the gap, which is difficult and moreover leads to a disturbingly obvious and unattractive join between the two ends of the spacer. In this case the join also remains a weak point in the otherwise reliable seal of the interior of the insulating glass pane.
It is known to close the gap in a plastic spacer, located in the vicinity of a corner, even before the insulating glass pane is assembled, by acting on the corner from both the inside and the two outer sides with three separately movable shaped elements. This yields a better join between the two ends of the spacer, but with considerable complexity in terms of equipment and above all time, which leads to a lengthening of the cycle time of the apparatus which applies the spacer onto the glass panel.
In the case of both procedures known from the related art, it is disadvantageous that the gap initially existing between the ends of the spacer is not reproducible, since irregularly shaped abutting surfaces with varying spacing are formed.